Cellular stresses such as accumulation of misfolded protein in the endoplasmic reticulum (ER stress), nutrient deprivation, UV irradiation, and oxidative damage induce a program of gene expression designed to alleviate cellular injury. An important contributor to stress gene expression is a family of protein kinases that phosphorylate eukaryotic initiation factor -2 (eIF2). Phosphorylation of eIF2 reduces the activity of this translation factor, leading to regulation of general protein synthesis and induced translation of mRNAs important for stress remediation. This proposal focuses on the eIF2 kinase, PEK (PERK, EIF2AK3), that is activated in response ER stress. PEK phosphorylation of eIF2 enhances cell viability in response to ER stress via activation of multiple transcription factors, including ATF4 and NF-KB, that direct expression of genes involved in stress remediation or apoptosis. An aberrant ER stress response is associated with a range of human diseases, including diabetes, bone and liver disorders, and circulatory and neurological pathologies. This proposal addresses the mechanisms regulating the program of stress-related gene expression in response to ER stress, and its role in disease. We propose four specific aims. Aim 1 Characterize PEK control of gene-specific translation in response to ER stress. We will determine whether translation reinitiation or alternative translation mechanisms are important for synthesis of regulatory proteins in the PEK response pathway. Aim 2 Characterize the role of eIF2 phosphorylation in the regulation of NF-KB activity. We will characterize the molecular mechanisms by which PEK activates NF-KB during ER stress and compare it to alternative NF-KB regulatory processes. Aim 3 Determine the role of eIF2 phosphorylation in cytoprotection against anti-cancer drugs. In this aim, we will explore the link between the eIF2 kinase and p53 stress pathways, and determine whether eIF2 phosphorylation contributes to resistance to anti-cancer drugs. Aim 4. Determine the functional consequences of PEK mutations identified in the human population. We will characterize the functional consequence of PEK missense changes derived from WRS patients or polymorphisms using mammalian cultured cells. Together, addressing these aims will increase our understanding of the process of cellular adaptation to environmental stresses and its impact in human disease. [unreadable] [unreadable]